IL4IL13

IL4IL13 commonly refers to the cytokines interleukin-4 (IL-4) and interleukin-13 (IL-13), two closely related signaling proteins that coordinate type 2 immune responses. Both are produced by Th2 cells and several other cell types, including mast cells, basophils, eosinophils, and innate lymphoid cells, and they play key roles in humoral immunity, inflammation, and tissue remodeling. IL-4 is a driver of Th2 differentiation and promotes B cell class switching to IgE, while IL-13 supports IgE production and influences mucus secretion, airway hyperresponsiveness, and epithelial-milieu changes. The two cytokines have overlapping activities but also distinct effects depending on the tissue context.

Receptors and signaling: IL-4 signals through receptor complexes that include IL-4Rα. There are two main forms: a type I receptor (IL-4Rα with the common γ chain) and a type II receptor (IL-4Rα with IL-13Rα1). IL-13 signals mainly through the type II receptor, and there is a separate decoy receptor, IL-13Rα2, that binds IL-13 to limit its activity. Both cytokines activate JAK-STAT pathways, particularly STAT6, along with other signaling cascades such as PI3K or IRS-2 in some cell types.

Physiological and clinical relevance: IL-4 and IL-13 are central to allergic diseases and helminth defense. They contribute to eosinophilic inflammation, mucus hypersecretion, goblet cell hyperplasia, airway remodeling, and IgE production. Dysregulation is associated with asthma, atopic dermatitis, and chronic rhinosinusitis with nasal polyps. Therapeutically, targeting this axis (for example, via anti-IL-4Rα therapy such as dupilumab) can reduce signaling from both cytokines and alleviate disease activity. Genetic loci for IL4 and IL13 are located in distinct chromosome regions and contribute to individual variation in immune responses.